XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 253
by Batchelor et al. (2017) that rapid initial breakage of
large fragments may be likened to an effective reduction in
SAG mill F80, which can be modelled to predict processing
benefits. To the authors knowledge, no investigations have
been conducted to date around the effects of microwave
treatment on stirred milling and fine grinding. However, it
is logical to presume that as grinding becomes finer, single
phase grain breakage drives comminution energy require-
ment and any residual microwave fractures would be rap-
idly exhausted and likely not able to be measured.
Microwave treatment also lends itself to flowsheets that
prioritize dry processing. This makes microwave pre-treat-
ment for novel flowsheets, e.g., HPGR or impact crushing
combined with stirred mill circuits illustrated in Figure 5,
an interesting prospect. To the authors knowledge, there
have been no investigations into the impact of micro-
wave treatment on HPGR or impact crushing products.
However, any pre-treatment method that aids preferential
breakage (such as microwaves) might be expected to com-
pliment preferential breakage reported from these commi-
nution machines. Similarly, the goal would be to reduce ore
competency and the specific energy requirement to either
save energy or increase throughput.
Implementation of a new technology such as micro-
wave pre-treatment will likely begin as a bolt on to exist-
ing plants until the technology has reached a certain level
of maturity and industry acceptance. As such, assets will
already be in place and put constraints on how microwave-
induced fractures can be exploited. However, Batchelor et
al. 2017 discussed how further benefits can be unlocked if
microwave treatment is introduced into an unconstrained
environment as part of initial plant design. Therefore, con-
sideration of pre-treatment methods early in new mine stud-
ies, perhaps in conjunction with novel flowsheets (Engeco
2021), could help to bring the most benefit to industry.
Physical Separation
Direct comminution energy reductions have historically
been the main target for microwave-assisted breakage
research. However, microwave-induced fractures become
exhausted as particle sizes approach typical primary grind
sizes and coarser crushing and grinding reaps the main
benefits. Therefore, it is not surprising that the dramatic
reductions in Bond Work Index reported in early studies, at
very high and economically unfeasible microwave specific
energy inputs on ball mill feed, were not replicated at more
economically feasible energy inputs, on larger fragments
subsequently crushed to ball mill feed sizes.
Perhaps the greatest potential benefit lies not in direct
comminution energy reduction, but in increasing the pri-
mary grind size to effect liberation and recovery or achiev-
ing higher recovery at the existing primary grind size. A
grind size increase of as little as 10 µm in a typical SABC or
similar circuit, illustrated in Figure 6, can result in a signifi-
cant reduction in specific comminution energy. Increasing
valuable metal recovery with the same input energy and
Stirred
Mill
U/F
Cyclone
HPGR
MW
Impact
MW
Figure 5. Microwave system in dry and novel comminution
circuits
SAG Mill
ROM/Crush
MW
Screen
Cyclone
U/S
O/F
Recovery
Process
Flotation Conc.
Gravity Conc.
Tailings
Ball Mills
Crusher
U/F
O/S
Figure 6. Simple crush, grind and flotation or gravity circuit
with integrated microwave pre-treatment
O/F
by Batchelor et al. (2017) that rapid initial breakage of
large fragments may be likened to an effective reduction in
SAG mill F80, which can be modelled to predict processing
benefits. To the authors knowledge, no investigations have
been conducted to date around the effects of microwave
treatment on stirred milling and fine grinding. However, it
is logical to presume that as grinding becomes finer, single
phase grain breakage drives comminution energy require-
ment and any residual microwave fractures would be rap-
idly exhausted and likely not able to be measured.
Microwave treatment also lends itself to flowsheets that
prioritize dry processing. This makes microwave pre-treat-
ment for novel flowsheets, e.g., HPGR or impact crushing
combined with stirred mill circuits illustrated in Figure 5,
an interesting prospect. To the authors knowledge, there
have been no investigations into the impact of micro-
wave treatment on HPGR or impact crushing products.
However, any pre-treatment method that aids preferential
breakage (such as microwaves) might be expected to com-
pliment preferential breakage reported from these commi-
nution machines. Similarly, the goal would be to reduce ore
competency and the specific energy requirement to either
save energy or increase throughput.
Implementation of a new technology such as micro-
wave pre-treatment will likely begin as a bolt on to exist-
ing plants until the technology has reached a certain level
of maturity and industry acceptance. As such, assets will
already be in place and put constraints on how microwave-
induced fractures can be exploited. However, Batchelor et
al. 2017 discussed how further benefits can be unlocked if
microwave treatment is introduced into an unconstrained
environment as part of initial plant design. Therefore, con-
sideration of pre-treatment methods early in new mine stud-
ies, perhaps in conjunction with novel flowsheets (Engeco
2021), could help to bring the most benefit to industry.
Physical Separation
Direct comminution energy reductions have historically
been the main target for microwave-assisted breakage
research. However, microwave-induced fractures become
exhausted as particle sizes approach typical primary grind
sizes and coarser crushing and grinding reaps the main
benefits. Therefore, it is not surprising that the dramatic
reductions in Bond Work Index reported in early studies, at
very high and economically unfeasible microwave specific
energy inputs on ball mill feed, were not replicated at more
economically feasible energy inputs, on larger fragments
subsequently crushed to ball mill feed sizes.
Perhaps the greatest potential benefit lies not in direct
comminution energy reduction, but in increasing the pri-
mary grind size to effect liberation and recovery or achiev-
ing higher recovery at the existing primary grind size. A
grind size increase of as little as 10 µm in a typical SABC or
similar circuit, illustrated in Figure 6, can result in a signifi-
cant reduction in specific comminution energy. Increasing
valuable metal recovery with the same input energy and
Stirred
Mill
U/F
Cyclone
HPGR
MW
Impact
MW
Figure 5. Microwave system in dry and novel comminution
circuits
SAG Mill
ROM/Crush
MW
Screen
Cyclone
U/S
O/F
Recovery
Process
Flotation Conc.
Gravity Conc.
Tailings
Ball Mills
Crusher
U/F
O/S
Figure 6. Simple crush, grind and flotation or gravity circuit
with integrated microwave pre-treatment
O/F